The invention relates to the synthesis of polymers containing self-complementary quadruple hydrogen groups by copolymerizing monomers containing a quadruple hydrogen bonding group with one or more monomers of choice. The resulting polymers show unique new characteristics due to the presence of additional physical interactions between the polymer chains that are based on multiple hydrogen bonding interactions (supramolecular interactions).
This invention relates to polymers containing units that are capable of forming H-bridges with each other leading to physical interactions between different polymer chains. The physical interactions originate from multiple hydrogen bonding interactions (supramolecular interactions) between self-complementary units containing at least four hydrogen bonds (units capable of forming at least four hydrogen bonds are in this application abbreviated as 4H-units or 4H-monomers and are used in this application as interchangeable terms) in a row. Sijbesma et al. (U.S. Pat. No. 6,320,018; Science, 278, 1601) discloses such self-complementary units which are based on 2-ureido-4-pyrimidones. In Example X the 4H-unit 6-(3-butenyl)-2-butylureido-4-pyrimidone is disclosed. Polymers obtained by polymerization of the carbonxe2x80x94carbon double bond moiety of this compound are, however, not disclosed.
Telechelic polymers have been modified with 4H-units (Folmer, B. J. B. et al., Adv. Mater. 2000, Vol. 12, 874; Hirschberg et al., Macromolecules 1999, Vol. 32, 2696). However, this has been performed after polymerization in a laborious post-modification process. Another drawback of these polymers containing 4H-units is that they only contain the 4H-unit coupled at the ends of the polymers. Consequently, the number of end groups is therefore limited by the amount of end groups (normally 2), and the functional units are always located on the periphery of the polymer.
Polymers containing hydrogen bonding groups in the main chain synthesized via copolymerization of hydrogen bonding monomers have been obtained with hydrogen bonding units containing three H-bonds in a row (Lange F. M. et al., Macromolecules 1995, Vol 28, 782). However, only an alternating copolymer of styrene and maleimide can be used in this approach, and moreover, the H-bonding interactions between the polymers are much weaker than the H-bonding based on the 4H-units, obviously resulting in poorer material properties.
Polymers with quadruple H-bonding units in the main chain have been obtained by copolymerizing 4H-monomers in the main chain of a polyolefin (Coates, G. W. et al., Angew. Chem. Int. Ed., 2001, Vol. 40, 2153). However, complex chemistry has to be used to prepare and to polymerize the monomer and, due to the intrinsic sensitivity of the catalyst needed to obtain the polymer, severe limitations hinder the general use of this system and limits it to tailor-made polyolefin systems. For example, Coates et al. discloses the copolymerization of 1-hexene and a 6-hexenyl-2-ureido-4-pyrimidone derivative with a Ziegler-Natta type nickel based catalyst and diethylaluminum chloride as cocatalyst.
The present invention discloses a convenient synthesis and convenient copolymerization of monomers containing a 4H-unit with other widely available monomers. The present invention can be used for the preparation of a wide range of polymers with 4H hydrogen bonding units in order to provide these polymers with unique new material properties as a result of the incorporation of the 4H-units. These new material properties result from the reversible nature of H-bonding interactions between the polymer chains that allow reversible changing of the material properties by external stimuli like heat or dilution. Consequently, it becomes possible to prepare materials that combine the mechanical properties of conventional macromolecules with the low melt viscosity of organic compounds.
The invention relates to monomers comprising (a) a monomeric unit having a group that can be polymerized (or a monomeric unit having a polymerizable group), (b) a linking moiety and (c) a structural element capable of forming at least four hydrogen bridges, preferably four hydrogen bridges, wherein the monomer has the general structure:
(a)-(b)-(c).
The invention further relates to processes for the preparation of these monomers, copolymers comprising these monomers and processes for the preparation of these copolymers.